The polyphenylenethers and the processes for preparing same are known and described in several patents (for example U.S. Pat. Nos. 3,306,874; 3,306,875; 3,639,656; 3,642,699; 3,661,848; 3,733,299) in which there is described the use, as catalysts, of various copper salts with primary, secondary and tertiary amines, which allow, however, to obtain catalytic values (copper/monomer molar ratio) not exceeding 1:500.
With a view to attaining high catalytic values, a catalytic system was subsequently suggested (U.S. Pat. No. 3,914,266) consisting of cuprous or cupric bromide with N,N'-disubstituted diamines having 2-3 carbon atoms between the two nitrogen atoms, whose two substituents on the nitrogen atoms are isopropyl groups or alkyl groups, where the carbon atom bound to nitrogen is a tertiary atom.
Such catalyst system is used in the presence of great amounts of a bromide ions source, besides in the presence of a tertiary amine and, optionally, also of a secondary aliphatic amine. That is a complex catalytic system which involves, in particular, a wide use of bromide ions sources and of amine mixtures not easily recoverable.